Locking pin damping device



Aug. 3o, 1932. R J MER 1,875,096

LOCKING PIN DAMPING DEVICE Filed Aug. 21, 1929 il@ /17 f "m1 201m --16 mlilnhnllhl "1". /25

i ,24 diz @ab 3Q s@ 'Q1 a7 :g Q0 27 56 J9 a H 41 Z8 31.52 y0 Patented Aug. 30, 1932 PATENT OFFICEl Y RALPH llVHLLER, F MADISON, VT.K7IS C01\TSI1\`T, ASSIGNOR TO YGrISHOI/.l MACHINE COM- PANY, OF MADISON, WISCONSIN, A CORPORATION OF lWISCONSIN LOCKING PIN DAMPING DEVICE Application filed August 21, 1929. Serial No. 387,295.

rods, bars, shafts, and the like, the threads are customarily cut by a cutting tool mounted Von a tool post slide that is in turn mounted on a carriage slidable on and lengthwise of thelathe bed; the carriage, after the tool has made an initial cut on the work, being returned to starting position, the tool slide and tool slightly advanced to effect a deeper cut, and the carriage again advanced; these operations being'repeated until a thread of the desired or predetermined depth has been cut on the work. In such a method of cutting, it is, of course, necessary for accurate work, that each time the point of the cutting tool is engaged with thevwork it shall exactly register with a previously cut groove of the thread. To do this, it is necessary to stop the return or back traverse of the carriage at an exact point with reference to the groove being cut. A mechanical attachment to eii'ect this result is disclosed and claimed in Lettersv Patent to Edward F. McNutt, No; 1,749,598, March 4, 1980, owned by the assignee of the present application, and consisting essentially of a peripherally notched disc on or geared to the lead screw and a spring-actuated locking pin disposed radially of the disc and normally restrained'from engaging the latter, but released simultaneously vwith the disengagement of the lead screw drive so that during the further rotation of the disc under the inertia of the carl riage and lead screw the locking pin snaps into one of the notches of the disc and thus arrests the movement of the carriage at a point where the cutting tool will register with the groove being cut in the work.

Now, in practice it has been found that where the back traverse of the carriage is rapid and the disc rotates at high speed, the locking pin will not always remain in the lirst notch yit encounters and arrest the rotation of the disc but will ride over several notches until the speed ot rotation of the discy has suihciently slacliened, when it will snap into place and lock the disc against further rotation.Y This overrunning causes undue wear on the notches, and a severe pounding action which tends to injure the parts.

The main purpose of the present inven' tion is to provide means for preventing this injurious action, whether the device be employed to arrest the rotation of a lead screw of a lathe or other machine tool or any other carriage driving member; and the invention is based on the principle of damping or retarding the working movement ot' the locking pin 'until the speed of rotation of the notched disc has slowed down to such an extenty that the first notch thereof entered by the locking pin will not override the latter. f f

One simple form in which the invention may be embodied is illustrated in the accompanying drawing, in which the figure is an elevational view, partly in vertical section.

Referring to the drawing, 10 designates as anr entirety a stationary casing or housing, through which extends a shaft 11, which, in the case of a lathe, may be either the lead screw, or a countershaft geared to the lead screw as disclosed in the McNutt patent above identified.

Fast on the shaft 11 is a disc 12 with one .15 or more peripheral notches 13; four such notches being herein shown spaced ninety degreesr apart.

These notches are designed to interlock- -ingly cooperate with a radially-disposed u locking pin 14 that is slidably mounted in a hollow guide 15 on the lower side of the casing 10.' The guide 15 has a horizontal slot 16 near its lowervend, and the pin 14 has a registering slot 17 of slightly greater width than the slot 16.` Through the slots 16 and 17 extends a bar 18 formed on its lower side with an inverted V-shaped cam notch 19 that engages with a pin 2O mounted on the locking pin 14 crosswise of the lower portion of '00 the slot V17 of the latter. One end of the bar 18 is pivoted at 21 to van upstanding arm 22 fast on a rock 'shaft 23, the shaft 23, in case of a lathe,'having an operating connection'to a clutch through which the drive of thelead screw 11 is thrown in and out. In the position of the parts illustrated in the drawing, 'the lead screw drive has beenv disengaged,but when the bar 18 is moved to the lright, Iso as to retract the locking pin 14 W from the disc`12, the lead screw kdrive is thrown in as described in the McNutt patent above identified.

The locking pin is urged toward the periphery of the disc 12 by a thrust spring 24,

theupper end of which isfhoused in a recess in# the llower end of the locking pin, and the lower end of which is footed on a gland 26 hereinafter referred to.

I Describing now my'jimproved Adevice for damping or retarding the working stroke of the locking pin, 27 designates av hydraulic, '.cylinder, in which is fitted apiston 28. The

upper head of the cylinder is formed integral fit; vThe coil spring `24 encircles'the piston rod 30, as shown.

":The cylinder 27 contains two lateral ports .-34 and 35 at opposite ends thereof, which ports are connected bya passage 36 inthe I y 1. In a device for arresting the travel yof' a `machine tool carriage, the combination of a wall of the cylinder. The upper portion of this passage is enlarged, and is formed with a seat 37Jff'or a steel ball 38 constituting a .-checlrvalve which will allow fluid to pass L Vfreely from the lower end of the cylinder to the-Yupper'end,` but will prevent the passage .of the fluid inthereverse direction. ,A very small groove '.39 out in the cylinder wall, as shown, 'forms a restricted by-pass for the V.fluid from one side of the piston 28 to the other.

The holes shown at40 are for construc- .tional 'purposes only, and are closed by tape'rplugsi'41, as shown. .A similar taper plug 42 closes the upper end of the passage 36.

The icylindenports, and all the open spaces connected with it, are filled completelyV with a fluid, preferably oil. I i

'Assuming the application of the device to a lathe, at the starting of the rapid traverse movement'of the carriage,theloclring pin 14 isretracted from locking engagement with the'notched disc by the bar 18, and the lead screw isV freetorotate. This retraction of v the locking pin pushes the piston 28 downwardly in the cylinder and transfersfiuid fromthe spacebelow'the piston through they Y y'At the completion of the rapid traverse movement of thelathe carriage, by movement which thedevice is applied:

is left free, and its inward movement Vinto a y notch yunder the pressure of spring24 will raise the piston 28. Since the check valve38 blocks'the passage of fluid through passage 36 in a downward direction, the speed of" the upward movement ofthe' piston isretardedv and governed ,by the krate atwhich the f Y fluid can flow through Ythe restrictedrby-pass `,'Iheinertia kof the lead` screw-and carriage, when left free at the end of the rapid tra-` verse movement is sufiicient to continue the.

rotation'of the notched disc 12 for an api j-preciable length 'of time.V lThe retarding action'of the piston allows the speed of rotation of the disc to die down toa point where thelocking pinwill enter and lockingly engage one'l of the Vnotches of the disc without jar, vand also will previously pass over the intervening notch ory notches Ywithout vpartial engagement, such as sometimes' occurs where the upward movement ofthe pinis free. The

areafof therby-passto give the proper :speed is determined by eXperiment under the work- `to the inward ymovement of thelocking pin ing conditions of the particular machine to Y I claim:`Y

rotatable disc fast with van element of the car riage drive andf'ormedwith a lockingr recess of engagable with the periphery oiv said disc, a spring urging said pin towardlsaid disc, means lfor retracting said pin from'said disc whenv the carriage drive'is thrown in, a hydraulic cylinder having a piston andk piston rod connected to said locking pin, and means in said cylinder permitting a'free outward movement of said piston and `locking pin and retarding the inward movement thereof.

2. .In a device for arrestingthe travel of a machine tool carriage, the combination of a rotatable disc fast lwith anelement of the carriage drive and formedwith a locking recess in its periphery, a slidable .locking pin ldis'- posed radially of said disc withone end theref of engageable with'the periphery of said disc,

a spring urging said pin toward said disc,

`means for retracting said pin from said disc when the carriage drive is thrown in, a hydraulic cylinder having avp-iston and piston lrod connectedto said locking pin, a'flow paslstricted flow passage in said cylind'erf'connectingopposite ends of thelatter. u

aco

RALPH JQMI'LLER. Y

of the barV l18 tothe left, the locking pin 14 

